In a radio communications system, uplink time alignment (uplink TA) needs to be maintained after access of a user equipment (UE). An evolved Node B (eNodeB) configures an information element TimeAlignmentTimer (time alignment timer) for the UE by using radio resource control (RRC) signaling. Before the TimeAlignmentTimer times out, if the UE does not receive TA (time alignment) data, such as a TA MCE (MAC Control Element, media access control information element), sent by the eNodeB, uplink out-of-synchronization may occur on the UE.
In the prior art, when sending the TA data to the UE, the eNodeB needs to allocate physical downlink control channel (PDCCH) and physical downlink shared channel (PDSCH) resources. In addition, to ensure that the UE is free of uplink out-of-synchronization, the eNodeB needs to send the TA data to the UE periodically or upon an event trigger (when the eNodeB measures that TA needs to be adjusted) before the TimeAlignmentTimer times out, and it needs to schedule and allocate the PDCCH and PDSCH resources during each sending. This method consumes a lot of system resources and increases processing time of the eNodeB.